1. Field of Invention
This invention relates to an illumination device usable to produce a diffuse light.
2. Description of Related Art
The use of illumination devices such as book lights or general purpose task lights are well-known in the art. Typically, these devices may include a base, a neck portion and a light emitting portion emitting light in a desired direction. These devices may be used in situations where overall illumination of a room or environment is unnecessary or unwanted. These devices may also be used where a particular object or area requires additional or more intense illumination than the surrounding area. For instance, the pages of a book or a work area.
These devices may typically use incandescent or fluorescent light sources. Both of these sources suffer from a variety of problems. For example, incandescent lights may be fragile, have a relatively short lifespan, use a great deal of power and generate considerable heat that is capable of burning skin, upholstery and possibly creating a fire hazard. Incandescent lights are also susceptible to vibration and use a great deal of battery power, thus adversely affecting battery life. Further, current illumination devices such as book or task lights produce a light that is harsh on the user""s eyes, with a very bright illuminated spot at the center of the illuminated area which fades in intensity towards the periphery of the illuminated area. In some cases, if adequate shielding or shading is not provided from the bulb, the light may be blinding to the user.
While traditional fluorescent lights may tend to be cooler than incandescent lights they are fragile and are typically too large and bulky for smaller applications. Additionally, some fluorescent lights may also have hot areas at their terminal ends and at their inverters. Traditional fluorescent lights also tend to produce a flickering illumination as they age, causing a distraction to the user.
The illumination device of this invention produces a diffuse light by making use of an illumination panel. This illumination panel may utilize either a light guide or an electroluminescent (EL) source. This device may be either portable or stationary. In various exemplary embodiments of this invention the illumination panel may be rectangular in shape and have roughly the thickness of a credit card. However, it should be appreciated that the illumination panel according to this invention may be of any shape, size or thickness. For example, the illumination panel of this invention may have a thickness roughly equivalent to that of a sheet of paper.
An illumination panel having these characteristics provides several advantages over illumination devices of the prior art. For example, unlike incandescent or fluorescent lights that emit light from a relatively small area or point source, an illumination panel having a substantial area provides illumination in a more uniform fashion over a given area with low glare. A thin flat illumination panel allows the device of this invention to also be used as a book mark. A thin flat illumination panel also facilitates easy storage, decreases the overall weight of the device and may be more aesthetically pleasing to the eye. This may provide a particular advantage, for instance, to a book light or task light that is portable. As a lightweight task light or book light the illumination device can be easily positioned or fixed to an object such as a book, shirt pocket, computer, clip board; or work surface, etc. While the features of the illumination device may be small or compact in size, the same features may be applicable to lights of larger size and greater weight.
The term xe2x80x9clight guidexe2x80x9d refers to a device that receives light at an input end and propagates the light to an output end or side without significant losses. In general, light guides operate on the principle of internal reflection, whereby traveling light is reflected on the internal surfaces of the guide. The light emitting region of the light guide may either be at a distal end or at any point along its path based on the construction of the guide. Light may be extracted along its length prior to reaching the distal end by surface treatments such as chemical or mechanical abrasion, or the use of other internal materials to reflect light out of the guide. Light may also be extracted by bending the guide itself. Light guides may be illuminated by a variety of bulb types, as well as single bulbs, multiple bulbs or an array of bulbs. Examples of light guides include but are not limited to fiberoptic panels, which xe2x80x9cleakxe2x80x9d light due to a tight weave or surface alteration of the fibers, or formed polymer panels such as acrylic, with reflective surfaces. The light guides may also be solid or hollow in configuration. It should be appreciated that the device of this invention may utilize any type of light guide now known or known in the future.
Electroluminescent panels are self-contained devices that produce light upon the electrical stimulation of chemicals, for example phosphor. Due to the method of lighting, the illumination panel dimensions may be made very thin, for example, approximately the thickness of a sheet of paper. Compared to traditional incandescent or fluorescent light sources, electroluminescent panels provide the advantages of a more diffuse light, a smaller power requirement, lighter weight and ease of storage.
In various exemplary embodiments, the illumination panel of the device of this invention may be of any shape or curvature. The panel may be composed of either a light guide terminating in a panel or an electroluminescent panel. In other exemplary embodiments more than one panel may be used on a given light assembly. In still other exemplary embodiments, mirrored or reflective surfaces may be used to minimize light loss. Colored filters or lenses may also be included in other exemplary embodiments as a permanent or removable part of the assembly. The panel of this invention may also be used with traditional point or small area light sources.
These and other features and advantages of this invention are described in or are apparent from the following detailed description of the preferred embodiments.